In a known engine of the type described in German DT-OS No. 23 33 962, stratification of the charge in the working chamber is obtained by feeding a relatively lean fuel-air mixture through the inlet port and by blowing a fuel-vapor air mixture additionally into the working chamber. By means of such stratification of the charge the aim is to achieve both a reduction in the fuel consumption and also a substantial reduction in the pollutants in the exhaust gases. In this known construction it is arranged that the injection is directed into a recess in the rotating piston when the recess is opposite the sparking plug, which is placed well ahead of the second minor-axis node, the recess forming an increase in the cross-section of the volume in the neighborhood of the sparking plug for the purpose of slowing down the velocity of the flow. Stratification of the charge in a rotary piston engine with its combustion chamber having the shape of a sickle in cross-section, in which the relatively lean fuel mixture always has to be ignited by a rich mixture provided close to the sparking plug, cannot be relied upon to take place in all operating ranges under the given conditions, namely, a slowing down of the velocity of flow, as this can break down the rich mixture and can lead to variations in the fuel/air ratio which have an adverse effect on the stratification of the charge.
From German DT-OS No. 2 303 419 it is furthermore known to achieve stratification of the charge by providing an antechamber in the peripheral wall in the region of the second node, this chamber having a sparking plug and an injection nozzle and in which there is formed a rich fuel/air mixture, while the main working chamber contains a relatively lean fuel/air mixture formed by a carburetor or by a second injection nozzle. Such ante-chambers in the housing give rise to substantial thermal problems. Moreover, there are heat losses and transfer losses in the transfer of the ignited fuel/air mixture from the ante-chamber into the main working chamber through a relatively small opening, these losses reducing the power and increasing the fuel consumption under part-load conditions.